how to know what atoms donate a hydrogen bond

Learning Objective

• Depict the properties of hydrogen bonding.

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Fundamental Points

• Hydrogen bonds are strong intermolecular forces created when a hydrogen atom bonded to an electronegative cantlet approaches a nearby electronegative cantlet.
• Greater electronegativity of the hydrogen bond acceptor volition lead to an increase in hydrogen-bail strength.
• The hydrogen bail is one of the strongest intermolecular attractions, but weaker than a covalent or an ionic bail.
• Hydrogen bonds are responsible for holding together DNA, proteins, and other macromolecules.

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Terms

• hydrogen bondThe allure between a partially positively charged hydrogen atom attached to a highly electronegative cantlet (such as nitrogen, oxygen, or fluorine) and another nearby electronegative atom.
• electronegativityThe tendency of an atom or molecule to draw electrons towards itself, form dipoles, and thus form bonds.
• intermolecularA type of interaction between two different molecules.

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Forming a Hydrogen Bail

A hydrogen bond is the electromagnetic attraction created between a partially positively charged hydrogen cantlet attached to a highly electronegative atom and another nearby electronegative atom. A hydrogen bail is a type of dipole-dipole interaction; it is not a true chemical bond. These attractions can occur betwixt molecules (intermolecularly) or inside dissimilar parts of a unmarried molecule (intramolecularly).

Hydrogen bonding in waterThis is a space-filling ball diagram of the interactions between separate water molecules.

Hydrogen Bond Donor

A hydrogen atom attached to a relatively electronegative atom is a hydrogen bail donor. This electronegative atom is usually fluorine, oxygen, or nitrogen. The electronegative atom attracts the electron cloud from around the hydrogen nucleus and, past decentralizing the deject, leaves the hydrogen atom with a positive fractional accuse. Because of the pocket-size size of hydrogen relative to other atoms and molecules, the resulting accuse, though only partial, is stronger. In the molecule ethanol, there is one hydrogen atom bonded to an oxygen atom, which is very electronegative. This hydrogen atom is a hydrogen bond donor.

Hydrogen Bond Acceptor

A hydrogen bond results when this strong partial positive accuse attracts a lone pair of electrons on another atom, which becomes the hydrogen bail acceptor. An electronegative cantlet such as fluorine, oxygen, or nitrogen is a hydrogen bond acceptor, regardless of whether it is bonded to a hydrogen atom or not. Greater electronegativity of the hydrogen bond acceptor will create a stronger hydrogen bond. The diethyl ether molecule contains an oxygen cantlet that is non bonded to a hydrogen atom, making it a hydrogen bond acceptor.

Hydrogen bond donor and hydrogen bond acceptorEthanol contains a hydrogen atom that is a hydrogen bond donor because it is bonded to an electronegative oxygen atom, which is very electronegative, and then the hydrogen atom is slightly positive. Diethyl ether contains an oxygen cantlet that is a hydrogen bail acceptor considering it is not bonded to a hydrogen atom and then is slightly negative.

A hydrogen attached to carbon can also participate in hydrogen bonding when the carbon atom is bound to electronegative atoms, as is the example in chloroform (CHCl₃). As in a molecule where a hydrogen is fastened to nitrogen, oxygen, or fluorine, the electronegative atom attracts the electron cloud from around the hydrogen nucleus and, past decentralizing the deject, leaves the hydrogen atom with a positive partial charge.

Interactive: Hydrogen BondingExplore hydrogen bonds forming between polar molecules, such as h2o. Hydrogen bonds are shown with dotted lines. Show partial charges and run the model. Where exercise hydrogen bonds course? Try changing the temperature of the model. How does the pattern of hydrogen bonding explain the lattice that makes up water ice crystals?

Applications for Hydrogen Bonds

Hydrogen bonds occur in inorganic molecules, such as water, and organic molecules, such as DNA and proteins. The ii complementary strands of DNA are held together by hydrogen bonds betwixt complementary nucleotides (A&T, C&K). Hydrogen bonding in h2o contributes to its unique properties, including its high boiling bespeak (100 °C) and surface tension.

Water droplets on a leafageThe hydrogen bonds formed between water molecules in water aerosol are stronger than the other intermolecular forces between the water molecules and the leaf, contributing to high surface tension and distinct h2o droplets.

In biology, intramolecular hydrogen bonding is partly responsible for the secondary, 3rd, and 4th structures of proteins and nucleic acids. The hydrogen bonds help the proteins and nucleic acids course and maintain specific shapes.

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Source: https://courses.lumenlearning.com/introchem/chapter/hydrogen-bonding/

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